more smoke - electrical problem perhaps

[Vart]

do i read that oily smelling smoke rising from the right hand side (if in the driving street) of the engine and wet oily grot from what looks like the block sump join is the sump gasket giving up?

if so there may soon be a 340 being broken for spares - mostly run out of patience now - the car almost idles without huge amounts of black smoke but now driving with a fire extinguisher (thanks mac!) on the passenger seat because it smokes after less than a mile will soon become tiring.

does this sound like a sump gasket?

cheers

toby

[pettaw]

Toby, if you're getting oily smoke coming from parts of the engine I would be looking a lot higher up than the sump gasket. The sump may be weeping slightly at the join, but its so low down the engine that apart from looking messy I don't think it would cause any other problems.

I can't remember which side of the engine all the vitals are, but I would check the join between the fuel pump and the block, that's a favourite for oil leaks.

Your carb sounds like it needs serious attention if its smoking black smoke at idle.....Forgive me, I haven't been following your progress with it, I'll go back and read the thread and post up again.

[Vart]

smoke wise i don't think theres anything that side - header downwards theres nothing - how long does oil burn for should i have spilt a little into the header - i can't see any but with the smoke rising its hard to check for definate.

that the oil level has stayed the same leads me to think this could be the case but i don't want an engine fire cause i'm ignoring it.

would the block get hot enough after a while to burn oil sitting against it?

[Vart]

rocker cover was bent out of shape - i perhaps tighened too much.

regardless - if this wasn't sealing properly would the air getting in drag oil through the valves into the combustion chambers? i guess oil was leaking from this also causing the smoke.

the float has been adjusted according to haynes manual to 7mm from the gasket at maximum closed position (cover inverted and gap measured from gasket to near edge of float).

the vacuum feed into the renix is a little loose but i'm having some spares sent from home in suffolk for both a replacement renix and rocker cover (i've a replacement gasket) so hopefully these should sort out the problems.

is it worth going to a garage for a gas analyser tune for the idle? can't be much more than a 15 minute job?

see what you guys think about the rocker?

cheers

toby

[antiekeradio]

how did you check the float level?

the float should rest on the ball part of the needle, but it may NOT depress the spring inside the float needle.


an engine that smokes severely cannot be tuned with a screw only.

[Vart]

there was a gap between the rocker cover and the top of the edge letting oil leak out - i think this was causing most of the smoke.

exhaust soot wise - its got a little better but still smokes a lot coming off idle.

to adjust i inverted the cover so the float was resting upside down against the float valve and measured the gap between what is the top of the float if it was installed and the gasket. i set it too 7mm.

the floats 'free movement' between the float needle and its 'catch' is as standard (about 2mm) by guess work.

does this sound like the right proceedure? - its as given in haynes.

cheers

toby

[pettaw]

Wouter is right, you have to be very careful about the float height. There is a little ball spring on the needle itself. The Weber setting requires that the float rests against it, but doesn't depress it. Trouble is that the float on these carbs is quite heavy and will depress it if you rest the carb cover completely upside down.

The way to do it is to remeasure it making sure that the float is just touching the needle, closing it lightly but not with the ball part springing in.

BTW this is the reverse of the Solex carbs on the B172 and B200K models, where you let the float press the ball spring on the needle right down.

If the rocker cover was bent by overtightening, then you'll need to get another one from somewhere as this needs to seal properly to prevent oil getting out and also to rebalance the crankcase ventilation system, making the engine run poorly.

[jtbo]

Pettaw, in B200K ball valve should not be compressed either according to green book, picture shows how ball valve is not compressed and text says that "make sure ball valve is accurately positioned", is picture in that book misleading here?

Sorry from slight OT

[pettaw]

yeah, its misleading IIRC.

[jtbo]

yeah, its misleading IIRC.

Thanks, that is good info, Cisac I will now have my revenge upon you!

[Vart]

well i've been playing with it today again and after another carb strip and clean i'm becoming curious as to whether its at fault at all.

how does the car 'know' it should idling (idle solenoid in whatever position)?

if it never went into idle mode and was using that circuit of the carb what would the engine do? i've pulled the idle solenoid wire out whilst it was running and nothing happens..

would the vacuum through the tiny opening of butterfly 1 be enough to keep the car running and due to the pressure be pulling fuel / air in a bad mix through the main jets causing the rich running?

i had a trace of the wires in haynes and they end up at something called the 'bridge' at where i think the fuse box resides (other box beside full beam box?) if this died could the car simply not know when to idle. as this problem started very suddenly could electrics be the fault and an otherwise fine carb suddenly gives up?

i've swapped the rocker cover - i think the smoke is just grot i've spilt down the side of the engine that hasn't burnt off yet.

see what you think of my electrics theory?

cheers

toby

[nomead]

how does the car 'know' it should idling (idle solenoid in whatever position)?

if it never went into idle mode and was using that circuit of the carb what would the engine do? i've pulled the idle solenoid wire out whilst it was running and nothing happens..

would the vacuum through the tiny opening of butterfly 1 be enough to keep the car running and due to the pressure be pulling fuel / air in a bad mix through the main jets causing the rich running?

The way it normally works:

At idle the accelerator pedal isn't depressed at all, so the throttle butterfly is completely closed.

This would make the engine stop, but there's a bypass system that gives the engine just enough air and fuel to keep running - the amount is adjustable, here you have the idle mixture set screw and idle RPM set screw etc. (Actual implementations vary a bit though)

In an engine that's normally running, if you pull the wire off the idle solenoid, the engine should stop, and it should do that quite fast (within a second or two). That's what it does on mine after I sorted out some problems with the solenoid. It immediately cuts off any remaining fuel/air supply to the engine and the poor thing can't run without either of them.

(Also see the Green Book for B14 (02a), page 90 Idling and pick-up section)

i had a trace of the wires in haynes and they end up at something called the 'bridge' at where i think the fuse box resides (other box beside full beam box?) if this died could the car simply not know when to idle. as this problem started very suddenly could electrics be the fault and an otherwise fine carb suddenly gives up?toby

Yes, without electricity the solenoid should shut and after that there would be no idle. You can check it with a multimeter or test lamp, or whatever - with engine running, you should get +12V at the solenoid... if not, there's a problem somewhere

Some quick fault diagnostics for the solenoid: Remove it from the carb body. Carefully remove the idle jet from the end of it (small brass thing). It can be stuck in rather well so don't damage it - this little piece of metal is vital to the idle running of your engine. Now you should see the solenoid needle within the valve body. Give the solenoid some electricity (+12V to the connector, ground to the body) and the needle should move a short bit (1-2mm) in towards the solenoid body. Mine was stuck and needed some cleaning/oiling and now it works fine. "Refitting is a reversal of removal" as Mr. Haynes likes to say But check that the idle jet is reinserted so it's well seated within the solenoid body, that the o-ring seal outside the solenoid still 1) exists, 2) is made of rubber that's not perished yet, and don't over tighten! or you'll end up ruining the o-ring...

[Vart]

i see,

the solenoid is new (shiny new from weber rather than another carb) and sounds like its 'clicking' when the ignition is turned on.

from the green books it looks like the solenoid should divert fuel into the bypass passages emerging under the throttle in the first stage under idle conditions. the mixture for this is set by the mixture screw whilst the idle speed is simply a throttle stop adjustment.

if the idle solenoid never moved the jet into place / divert fuel would there be enough vacuum to pull fuel through the main jets allowing it to run very badly?

if so who runs the show? i had another trace of wires and they seem to arrive at plug 'B' (third from left looking from headlamps) in the fuse box. this is some sort of electrical whatnot but i lose the plot after there.

that it runs without an idle solenoid voltage is my current diagnosis of idle through the main jets plausible?

thanks for input

toby